Spark plug question

Discussion in 'Outboard Maintenance' started by KeepingItSimple, Jul 27, 2014.

  1. KeepingItSimple

    KeepingItSimple Well-Known Member

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    1983 merc 25hp
    Runs reasonably well. There are some idle issues that I've been trying to work on. I have replaced the spark plugs a couple of times now. After maybe 6-8 trips they look like this. When I change them the motor runs much better. I've never seen an outboard do this before. Any ideas? I am using the plug that is recommended for the motor. Almost like they are running too hot?

    These plugs were new a month ago:
    [​IMG]
     
  2. DuckNut

    DuckNut Brandon, FL

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    Looks like the plug if firing fine but you are getting water under the cowl- either from spray or when washing.

    Clean everything and spray it with a corrosion inhibitor.
     

  3. Tommysmicroskiff

    Tommysmicroskiff I Love microskiff.com!

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    Everything duckNut said plus look for a stainless steel equivalent plug

     
  4. Tommysmicroskiff

    Tommysmicroskiff I Love microskiff.com!

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    Here you go :) the 5939 QL87YC

    http://www.fishing-catalog.com/other%20products/spark_plugs.htm
     
  5. Brett

    Brett > PRO STAFF <

    Also check for a gasket leak/bleed dripping from top to bottom.
    I've had that happen between the water cover and cylinder head.
    Salt deposits will lead to the source.